This invention relates to means for reading an optical pattern containing one-dimensional or multi-dimensional characters.
Known optical reading equipment is used to read optical patterns by projecting a light onto the optical pattern. A light image reflected from the optical pattern is then projected onto an electronic scan type sensor, such as a photodetector, which converts the reflected light image into an electronic analog signal. The analog signal is then processed to read and recognize the optical pattern information.
A common optical pattern to be read is a barcode, comprised, typically, of a row of parallel stripes which may be, for example, black and white stripes of different shapes and with different spacing. However, use of optical reading apparatus is expanding in many fields, including, for example, various fields such as factory-automation, distribution channel, service system, etc. Furthermore, the volume of information to be recorded, read and processed is ever increasing. The increase in the information makes it difficult, if not impossible, to include the needed information in one row of a barcode. Therefore, it is now desirable to be able to read multi-row barcodes, 2-dimensional barcodes, letters, characters, and other high density codes.
Multi-dimensional information codes and symbols may be read by a scanner such as a TV camera system illustrated in FIG. 1. The TV camera system scanner in FIG. 1 includes a TV camera (21), an image processor (22) and a TV monitor (23). The image processor (22) is connected to a host computer (not shown) via a communication RS-232C line. In this kind of system an information label (24) is set to face the TV camera (21) and may be photographed by the TV camera (21) under normal room light illumination, and the photographed image is processed and converted by the image processor (22) and transmitted to the host computer. On the other hand, the data of the photographed image may also be displayed on a TV monitor (23) via a connecting cable.
Some problems associated with the prior art include the following: First, the TV camera (21), the image processor (22) and the TV monitor (23), etc. are expensive pieces of equipment. Second, a certain length of time is needed to prepare and focus the TV camera (21) to enable it to comply with the room illumination brightness. Third, a 2-dimensional area sensor, that converts the image of the TV camera (21) photoelectrically, has a limited effective number of pixels in the horizontal and vertical directions (e.g., 576Hxc3x97485V). This limits the resolution capacity of the reading. In this respect the resolution capacity is meant for a minimum line width of a readable information pattern. Fourth, the reading apparatus, repeating the rotation of a mirror in such a function as stop-rotation-stop, is slower in its reading speed and its improvement is fundamentally difficult.
It is an object of the present invention to overcome problems associated with the prior art discussed above.
It is another object of the invention to use a line image sensor and to effectuate a high speed, two-dimensional, reading of an optical pattern by cyclically varying and moving the angle and/or the position of a movable reflecting mirror.
It is still another object of the invention to enable the accurate reading in a very short time of a xe2x80x9cone-rowxe2x80x9d barcode as well as multi-row barcodes, 2-dimensional barcodes, letters and characters.
It is another object of the invention to enable the easy and accurate position setting and support of the reading apparatus and the aiming of the apparatus toward an object to be read.
It is another object of the invention to make use of a line image sensor having a large number of pixels arranged in a row to enable the reading of an optical pattern with greater resolution than can be done with conventional reading method by a TV camera.
Another object of the invention is to achieve fast reading of an optical pattern by the repeated back and forth movement and/or vibration of a movable reflecting mirror without a move-and-stop function.
Another object of the invention is to provide optical reading apparatus which is smaller in size, lighter in weight and less costly to manufacture than the prior art apparatus and which includes simplified and energy-saving means for providing swinging and/or vibratory motion.
An optical reading apparatus embodying the invention includes a housing with a rotatable optical unit mounted within the housing. The rotatable optical unit is mounted so it can rotate back and forth in a see-saw like fashion. The rotatable optical unit includes a light source, a reflecting mirror and a linear one-dimensional image sensor. The light source is used for illuminating an optical pattern located externally to the housing. The mirror means is arranged to receive light reflected from an optical pattern and to sequentially scan, one segment at a time, the entire area of the optical pattern. As the movable mirror means scans or sweeps across the optical pattern image it sequentially projects different narrow rectangular portions of the optical pattern area onto the linear image sensor, whereby the entire optical pattern image is projected one segment at a time onto the image sensor.
In a particular embodiment of the invention, the image sensor is a high density solid state charge coupled device (CCD) having a large number of pixels formed along one row.
In a particular embodiment of the invention, the mirror is mounted within a movable case mounted on a shaft to selectively cause the movable case and the mirror to go back and forth in a seesaw-like fashion. As the mirror goes back and forth, it sweeps or scans across the reflected image of the optical pattern sequentially projecting a narrow rectangular portion of the reflected optical pattern onto the linear image sensor.
In a particular embodiment, the light source for illuminating the optical pattern is also mounted within the movable case, with the light source arranged to illuminate the area of the optical pattern about to be read.
Driving means may be coupled to the shaft to cause it to swing back and forth or to rotate.
As to light reflected from the optical pattern and projected onto the movable mirror, an optical assembly may be used to collect the light reflected from the movable mirror and to project it via the optical assembly onto the linear image sensor.
In a particular embodiment, the light source, the mirror, the optical assembly and the image sensor are all mounted within the movable case and go back and forth together.
The output signals of the linear image sensor may be applied to signal processing circuitry which is, in turn, connected to a memory and decoding circuitry.
It should be noted that imparting a cyclical bending vibratory motion to the arm causes a reflecting mirror connected thereto to cyclically change angle and position, which in turn produces a scan pattern of parallel lines of approximately equal spacing from the optical pattern being read and which parallel lines are then projected onto the linear image sensor.
The light source illuminating the optical pattern is located outside of the reflected light path so as not to interfere with the light reflected from the optical pattern which is to be projected onto the linear image sensor.